Install trusty kernel from package manager

The version previously installed was used in lieu of the package manager
version due to it not being available in the package manager at the time.

The minimum version we now want is available in the package manager, so we're
returning to using the package manager.

Signed-off-by: Adam Stegman <astegman@pivotallabs.com>
Move a CPI lifecycle test out of a let block

Signed-off-by: Adam Stegman <astegman@pivotallabs.com>
Update OpenStack CPI lifecycle spec teardown

Wait for Piston to release the IP between runs.

Signed-off-by: Adam Stegman <astegman@pivotallabs.com>